Oom Hennie came up with a brilliant information. The use of milkfilter socks.
I thought, it might be interesting for everybody who could plumb in this kind of prefilter. Especially the LFS should think about it, because the milkfilter socks are so fine, I don´t think parasites like MI will pass. If MI breaks out, it will not spread into all the other tanks from the same system.

The prefilter has to be plumbed into the overflow pipe. In my case, into three central overflow pipes. All the water coming back to the sump has to pass the filtersock first. All waste products get caught in the filtersock before breaking down to nitrate and phosphate. Cleaning tanks in now fun, because everything can go down the overflow. Aptasia can´t spread any more, free carbondioxide gets taken out and the water gets enriched with oxygen.

The most important requirement for this kind of filtration are easy maintenance and little running costs.

The mik filter sock I use, are 90mm wide by 700 mm long. Both ends open.
My first trial was with a sock, cut in three equal pieces. 233mm long. Didn´t last for 24 hours in my growout system. The second trial was with a half sock, 350 mm long.
Last for around 18 to 20 hours. The long sock last for 24 hours in the broodstock system with 5 tanks and the short sock last for 24 hours in the broodstock system with 3 tanks.

The square silver bucket is a normal dustbin and I skip the part how to drill a hole in the bottom and to fit a tank connector or something similar. Everybody should know how to do it.

I paid for 100 milk filter socks 90 x 700mm, 110 Rand. Cut in half, which will be efficient enough for any normal system, will reduce the price for each sock down to
55 cents. 55 cents per day and you can throw the used sock away. Little running costs!

Changing the sock had to be easy and quick, otherwise it becomes a burden.

So I had to buil something, where the sock holder can slide in and with the use of two sock holders, changing the sock will take 2 seconds!

I found this piece of acrylic in my garage, so I bend it to a sort of a bracket that fits over the edge from the bucket(dustbin).

That´s how I build the sock holder.
A normal stop end 110mm and 50mm, and a ring cut off from a 50mm connector.

Cut a 53mm hole into the 110mm stop end and a 40 mm hole into the 50mm sto end.
Cut off a ring from a 50mm connector.
Cut off a piece of around 15mm from the 50mm stop end.

That´s how the holder needs to be glued together.

That´s how the sock holder will fit into the bracket.

The bracket needs to be cut like that, so that the sock holder can be easily changed.

The one end of the sock has to be closed with a small cable tie and the other end has to be turned over like a hem.

The sock has to be pushed in from the top down, so that the hem is over the edge of the 50 mm stop end.

Now the sock has to be secured with the ring from the 50mm connector.

Now the holder slides easily into the bracket and if the sock is clogged up, the water will flow directly over the edge of the 110mm stop end into the bucket(dustbin).

Here are a few used socks. None of them were longer in use than 24 hours!

The result is just amazing. Imagine all waste products, fishlarvae/shrimplarvae, floating algae or nori pieces, aptasia larvae, parasites, etc. gets caught and taken out on a daily basis.

Special thanks to Oom Hennie. Without him, I never would have known, that a milkfilter sock exists and I never would have build this fantastic pre filter, which is so easy to handle!

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Very important: If you build your own prefilter (milkfilter) you have to make sure, that the sock never can block the outlet. My socks are a bit longer than the depth of the filter and they could block the outlet, without any modifications!

I wrote: ...so I bend it to a sort of a bracket that fits over the edge from the bucket(dustbin).

I have to add the following important advice!

You are asking me for the adhesive I used. The reason why I did not use an adhesive is simple but very important.
If the adhesive comes loose and there is a big chance it will come loose, the sock would block the outlet and causing a flood. Do not glue the bracket in!

The filter in the pictures is used with around 6 to 8000 litre/hour. The force down, from the flowing water is strong and I strongly advice to mount the bracket like I did or to use screws to mount the bracket!

I wrote: ...so I bend it to a sort of a bracket that fits over the edge from the bucket(dustbin).

I have to add the following important advice!

You are asking me for the adhesive I used. The reason why I did not use an adhesive is simple but very important.
If the adhesive comes loose and there is a big chance it will come loose, the sock would block the outlet and causing a flood. Do not glue the bracket in!

The filter in the pictures is used with around 6 to 8000 litre/hour. The force down, from the flowing water is strong and I strongly advice to mount the bracket like I did or to use screws to mount the bracket!

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Thanx & sorry I think that maybe I missed that bit! Thanx again Luckyfish

Good one. I also have a 'pre-ilter' which is fitted between the overflow and the skimmer / dsb. I use 8 sheets of filterwool and replace all of it once a week. It's incredible the amount of 'stuff' it takes out. I certainly think this kind of pre-filter is an absolute must in one's system. I was looking for a sock type material but could not find something suitable. From your thread I now have the info I was looking for.

Tim, it's good to have such pre filter as you got, but replacing it once a week allows the caught waste products to break down into nitrate and phosphate.
For a reef tank not a problem if the filter can keep up.
Now it is possible to change a prefilter on a daily basis.

Good day.
Any idea were I can get it in Pretoria?
I have been googling but could not find anything.

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You can buy this cloth at any shop that sells material if you want to make your own, just ask for "melkdoek" they will know what it is.I've been using this for a month or so, when used i just throw it away and fit a new one. Price R30 per running/mtr, cut and stitch your own socks, i made about fifty and only used a bit more than half. Good luck.

You can buy this cloth at any shop that sells material if you want to make your own, just ask for "melkdoek" they will know what it is.I've been using this for a month or so, when used i just throw it away and fit a new one. Price R30 per running/mtr, cut and stitch your own socks, i made about fifty and only used a bit more than half. Good luck.

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That is wrong. The cloth you are talking about is probably the same they use to make cheese.
This material is very strong and the "mesh size" (it does look not like a mesh) is probably around 20 to 30 micron.

It is definately the best filtration I ever build! The results are fantastic.
FransSny put ne of these socks on his cube overflow. The sock got clogged within not even a day and the water clarity improved a lot.